The present invention relates to marine dock accessories, and more particularly to fender devices such as camels that are used for cushioning dock structure from being impacted by moored ships and other watercraft.
Camels are generally cylindrically shaped floating objects that are tethered alongside dock structure such as pilings. Traditionally, camels are large logs having a spaced pair of transverse openings bored therethrough, respective tethering chains or other flexible members that are suspended from the dock extending through the openings to corresponding weights that apply tension to the chains. The camel is guided in proximity to the pilings by sliding contact with the chains during changes in water level as are normally associated with tides, waves, and the like.
Wood as a material of camels and fender pilings is plagued by wear and tear as well as being attacked by wood boring marine organisms. Wood pilings and camels are typically treated with creosote (toxic), but even this material can be ineffective against modern marine borers. These marine borers can only be stopped by wrapping the wood pilings in plastic coverings. However, thin plastic coverings cannot withstand much wear and tear, especially abrasion from normal vessel contact. So wooden fender members often have thick plastic wrappings, which are expensive to provide. Moreover, the thick plastic wrappings of the prior art are ineffective in excluding parasites; therefore, the thick plastic coverings are typically used in combination with a thin plastic wrap, with a further cost penalty.
Concrete and steel are conventionally used as replacements for wood in pilings, telephone poles, and the like. However, these alternative materials have disadvantages, particularly as applied to camels. Concrete and steel pilings, for example, are heavy and awkward to maneuver. Neither concrete nor steel pilings make good fending pilings because neither is "forgiving" when impacted. Under impact, steel bends and buckles and concrete shatters. Both concrete and steel pilings are expensive to repair. Furthermore, steel, either standing alone or as a reinforcement in poured concrete, is subject to corrosion. Due to the weight of steel pilings, they can be difficult to transport.
U.S. Pat. Nos. 5,051,285 and 5,180,531 to Borzakian disclose a composite structure for pilings and telephone poles, including a tubular steel core and a thick molded plastic covering. The structure of Borzakian is unsuitable for camels for a number of reasons, including the following:
1. It is ineffective for cushioning in that the steel core extends to or beyond both end extremities of the plastic;
2. It is subject to deterioration in that water is not excluded from the interior of the core, and in that the plastic coating is subject to cracking during cooling in the molding process;
3. It is ineffective for use as a camel in that the plastic coating is not sufficiently buoyant for floating the structure.
Thus there is a need for a camel that is not subject to deterioration, that is effective for protecting docks and tethered watercraft from impact damage, and that is economical to produce.